diff --git a/api/.env.example b/api/.env.example
index 0d6b52a..7dfd995 100644
--- a/api/.env.example
+++ b/api/.env.example
@@ -2,6 +2,10 @@
 # any of these — keys live only in the proxy (charter §4).
 
 # Where the proxy sends model calls in dev (Ollama on the homelab).
+# Running the proxy IN DOCKER with Ollama on THIS host? localhost points at the
+# container, not the host — use http://host.docker.internal:11434 instead
+# (docker-compose.yml maps that name via host-gateway). Bare-metal/venv: keep
+# localhost. Homelab Ollama: use its address.
 OLLAMA_BASE_URL=http://localhost:11434
 
 # Prod model provider (charter §4). Leave blank in dev.
diff --git a/docker-compose.yml b/docker-compose.yml
index 51e913b..37b241c 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -14,6 +14,12 @@ services:
         required: false
     environment:
       PORT: 8000
+    # Reach a host-run Ollama from inside the container. On Linux, localhost in
+    # the container is the container itself, so OLLAMA_BASE_URL must be
+    # http://host.docker.internal:11434 (set in api/.env); this maps that name
+    # to the Docker host. Harmless when Ollama is on the homelab instead.
+    extra_hosts:
+      - "host.docker.internal:host-gateway"
     # Mount source + prompts + schemas so edits are live without a rebuild.
     # Prompts are source code (§16) — editing a prompt should reload like code.
     volumes: